1. Field of the Invention
The present invention relates to an internal combustion engine control apparatus capable of detecting an ignition timing in an compression-ignition internal combustion engine.
2. Description of Related Art
As such a control apparatus, there is a one that detects a pressure within a combustion chamber (in-cylinder pressure) by use of an in-cylinder sensor, and detects an ignition timing on the basis of the output value of the in-cylinder sensor. In this control apparatus, an energy generation rate (a heat generation rate) in the combustion chamber is calculated on the basis of the output of the in-cylinder sensor, and an ignition timing is detected on the basis of the calculated energy generation rate. A timing at which the heat generation rate (energy generation rate) exceeds a predetermined threshold value may be determined as the ignition timing.
However, the inventors of this application have found such a phenomenon that the heat generation rate re-increases after the heat generation rate increases and then decreases by fuel injection. This phenomenon can occur when there occurs a premixed combustion in a diesel engine, for example. In this case, the timing at which the heat generation rate exceeds the predetermined value cannot be determined as the ignition timing, because the heat generation rate exceeds the predetermined threshold value multiple times.
Japanese Patent Application Laid-open No. 2005-351161 discloses an internal combustion engine control apparatus as described above.